I. Field of the Invention
The subject matter disclosed herein relates generally to image processing.
II. Background
The creation of digital images is often constrained by inherent hardware limitations of the camera, lens and sensor. For example, a camera sensor may have a limited luminance dynamic range due to the small form factor of the sensor or the cost to produce a more extended dynamic range sensor. However, while the limits of many camera sensors is about two orders of magnitude, the dynamic range of real world scenes may be up to ten orders of magnitude. Being attached to an inexpensive or small fixed focal length lens that may not provide a wide angle of view, or may not be able to capture an entire scene in focus further hampers output image quality from digital cameras.
However, digital cameras are increasingly becoming integrated with relatively powerful processors (e.g., when integrated with a smartphone, or professional digital camera). Integration with a powerful processor can extend previously limited hardware to new capabilities. For example, as a result of the limited dynamic range offered in many camera sensors and newly available improved image processing capabilities, High Dynamic Range (HDR) image generation can be used to greatly increase the dynamic range of an output image. HDR combines multiple Low Dynamic Range (LDR) images captured with different exposure settings (e.g., by changing shutter speed while keeping the aperture the same, or by changing the sensor gain—ISO, or a combination of one or more exposure settings). For example, one image may be captured with a half second exposure, a second image at a one second exposure, and a third image at three seconds of exposure. In another example, a first image may be captured at ISO 100 (or equivalent sensitivity), a second image may be captured at ISO 200, and a third image may be captured at ISO 400. The three images with varied exposure settings can be combined using the properly exposed sections from each of the images to create a final output image.
A limitation of existing techniques that combine multiple input images to create a merged output image is the potential for ghost/ghosty artifacts, or “ghosting” in the final output image when a moving object is in the input image. Because moving objects are commonly present in real world image capture situations, improved multiple image processing techniques are desirable.